System and method for guard band utilization for synchronous and asynchronous communications

ABSTRACT

Embodiments are provided for guard band utilization for synchronous and asynchronous communications in wireless networks. A user equipment (UE) or a network component transmits symbols on data bands assigned for primary communications. The data bands are separated by a guard band having smaller bandwidth than the data bands. The UE or network component further modulates symbols for secondary communications with a spectrally contained wave form, which has a smaller bandwidth than the guard band. The spectrally contained wave form is achieved with orthogonal frequency-division multiplexing (OFDM) modulation or with joint OFDM and Offset Quadrature Amplitude Modulation (OQAM) modulation. The modulated symbols for the secondary communications are transmitted within the guard band.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/821,575, entitled “System and Method for Guard Band Utilization forSynchronous and Asynchronous Communications” filed Aug. 7, 2015, whichis a continuation application of U.S. patent application Ser. No.14/180,147 entitled “System and Method for Guard Band Utilization forSynchronous and Asynchronous Communications” filed Feb. 13, 2014 (nowU.S. Pat. No. 9,137,074 issued Sep. 15, 2015), all of which are herebyincorporated by reference as if reproduced in their entireties.

TECHNICAL FIELD

The present invention relates to the field of wireless communications,and, in particular embodiments, to a system and method for guard bandutilization for synchronous and asynchronous communications.

BACKGROUND

Orthogonal frequency-division multiplexing (OFDM) is a method ofencoding digital data on multiple carrier frequencies. The OFDM schemeis currently deployed in broadband multicarrier communications. However,OFDM suffers from high out of band (OOB) radiation due to the use of asquare pulse (e.g., a sine function in frequency domain) on eachsubcarrier. A guard band can be used to avoid interference between twobands due to OOB radiation. Filtered OFDM (F-OFDM) is a scheme in whicha filtering is applied to a sequence of OFDM symbols to reduce OOBradiation. The F-OFDM scheme has benefits of OFDM, e.g., simpleequalization, channel estimation, and suitability for multiple-input andmultiple-output (MIMO) transmissions. OFDM/Offset Quadrature AmplitudeModulation (OQAM) is a filter bank scheme which uses a time/frequencylocalized pulse shaping to yield a spectrally contained waveform. Thisscheme provides a relatively well contained spectrum and is suitable forsynchronous/asynchronous communications. In the OFDM scheme, the guardband is not exploited for data transmission, which results in loss ofspectral efficiency. There is a need for a scheme that allowsopportunistic radio communications and improves spectral efficiency forsynchronous/asynchronous communications.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the disclosure, a method increasingband utilization by a network component in a wireless network includesallocating secondary communications to a guard band. The guard bandseparates data bands assigned for primary communications and has asmaller bandwidth than the data bands. The method further includesmodulating, at the network component, symbols for the secondarycommunications with a spectrally contained wave form. The spectrallycontained wave form has a smaller bandwidth than the guard band. Thenetwork component transmits the modulated symbols for the secondarycommunications within the guard band.

In accordance with another embodiment of the disclosure, a networkcomponent for increasing band utilization in a wireless network includesat least one processor and a non-transitory computer readable storagemedium storing programming for execution by the processor. Theprogramming includes instructions to allocate secondary communicationsto a guard band. The guard band separates data bands assigned forprimary communications and has a smaller bandwidth than the data bands.The programming further configures the network component to modulatesymbols for the secondary communications with a spectrally containedwave form. The spectrally contained wave form has a smaller bandwidththan the guard band. The network component is further configured totransmit the modulated symbols for the secondary communications withinthe guard band.

In accordance with another embodiment of the disclosure, a methodincreasing band utilization by a network component in a wireless networkincludes receiving secondary communications within a guard band. Theguard band separates data bands assigned for primary communications andhas a smaller bandwidth than the data bands. The network componentfurther detecting, in the received secondary communications, symbolsmodulated according to a spectrally contained wave form. The spectrallycontained wave form has a smaller bandwidth than the guard band.

In accordance with yet another embodiment of the disclosure, a networkcomponent for increasing band utilization in a wireless network includesat least one processor and a non-transitory computer readable storagemedium storing programming for execution by the processor. Theprogramming includes instructions to receive secondary communicationswithin a guard band. The guard band separates data bands assigned forprimary communications and has a smaller bandwidth than the data bands.The programming includes further instructions to detect, in the receivedsecondary communications, symbols modulated according to a spectrallycontained wave form. The spectrally contained wave form has a smallerbandwidth than the guard band.

The foregoing has outlined rather broadly the features of an embodimentof the present invention in order that the detailed description of theinvention that follows may be better understood. Additional features andadvantages of embodiments of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example of a time windowing operation to smoothdiscontinuity between OFDM symbols;

FIG. 2 illustrates an implementation of a filtered time windowing OFDMtransmitter system;

FIG. 3 illustrates an embodiment of a guard band availability scheme;

FIG. 4 illustrates an embodiment of a guard band utilization scheme;

FIG. 5 illustrates another embodiment of a guard band utilizationscheme;

FIG. 6 illustrates an embodiment of a method for guard band utilizationfor synchronous and/or asynchronous communications; and

FIG. 7 is a diagram of a processing system that can be used to implementvarious embodiments.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

Embodiments are provided herein for guard band utilization forsynchronous and asynchronous communications. Specifically, spectrallycontained waveforms are used for communications in the guard bands,which separate primary data bands of the system to account for OOBradiation. Due to the spectrally contained waveforms, the guard bandscan be used for secondary communications, thereby increasing thespectral efficiency of the system. For instance, the primary system canuse OFDM or its variant, e.g., discrete Fourier transform-spread OFDM(DFT-S-OFDM) or Filtered OFDM (F-OFDM), for communications in theprimary data bands. A primary band is at a center of a primarybandwidth, which also includes two guard bands on the edges of theprimary data band. The secondary system can use the spectrally containedwaveforms in the guard bands. The primary system provides primaryservices or data channels for users of the primary system, and thesecondary system provides secondary services or data channels todifferent users. Alternatively, the secondary system can be used insignaling or other applications for the primary system. The primaryservices or data channels may have higher quality or priority than thesecondary services or data channels.

The spectrally contained waveforms include schemes such as F-OFDM andOFDM/Offset Quadrature Amplitude Modulation (OQAM). For example, theF-OFDM is used for synchronous communications. The OFDM/OQAM is used forsynchronous and asynchronous communications. Further, the secondarysystem are aware of the primary system and the secondary communicationsusing the spectrally contained waveforms in the guard bands can beconfigured to avoid interference with communications in the primary databands. FIG. 1 shows an example of a time windowing operation 100 tosmooth discontinuity between OFDM symbols. The time windowing (TW)operation 100 is used to smooth the transitions (discontinuity) betweenconsecutive OFDM symbols to prevent a high OOB.

FIG. 2 shows one possible implementation of a filtered time windowingOFDM (F-TW-OFDM) transmitter system 200. The F-TW-OFDM is oneimplementation of the general F-OFDM scheme. The transmitter system canbe part of a user equipment (UE) or a base station in a wirelessnetwork. As used herein, the term base station refers to any radioaccess node capable of communicating wireless signals with UEs or otherwireless communications devices. For example, a base station may be aNodeB as defined in Universal Mobile Telecommunications Systems (UMTS),or an eNodeB as defined in Long Term Evolution (LTE) systems. In theprocessing chain in the F-TW-OFDM transmitter system 200, each OFDMsymbol is first time-windowed according to the time windowing operation100. The resulting signal (the sequence of TW-OFDM symbols) is thenpassed through a pulse shaping filter. However, due to the linearfiltering, the filtered signal is expanded in time. In practice, thetruncation is performed on the signal to reduce such time expansion (toreduce overhead). However, the truncated signal has abruptdiscontinuities at the signal edges, resulting in high OOB. Therefore,another TW process (Edge TW) is needed to smooth out the edges of thetruncated signal.

FIG. 3 shows an embodiment of a guard band availability scheme. In thescheme, multiple primary assigned bandwidths, each including a primarydata band surrounded by guard bands. The data bands are used by theprimary system, e.g., with OFDM or F-OFDM. The guard bands are used bythe secondary system with F-OFDM, OFDM/OQAM or other spectrallycontained waveforms. The guard bands on each side of a data band can beused individually as a single band to carry secondary information.Alternatively, two adjacent guard bands belonging to two consecutivedata bands can be combined into a single band for the secondary system.Examples of available guard bands in Long Term Evolution (LTE) systemsinclude guard bands with 0.16 MHz on each side of a data band in 1.4 MHzprimary bandwidth, and guard bands with 1 MHz on each side of a databand in 20 MHz primary bandwidth. Other examples are shown in FIG. 3.

FIG. 4 shows an embodiment of a guard band utilization scheme.Specifically, a primary system can use OFDM symbols in the data bands,and a secondary system can use a spectrally contained waveform, such asF-OFDM symbols or OFDM/OQAM symbols, in the guard bands. FIG. 5 showsanother embodiment of a guard band utilization scheme. Specifically, aprimary system can use F-OFDM symbols in the data bands, and a secondarysystem can use a spectrally contained waveform, such as F-OFDM symbolsor OFDM/OQAM symbols, in the guard bands. In the embodiments above, theOFDM symbols can be F-OFDM symbols. This allows limited OOB radiation tothe secondary system. Further, the use of the spectrally containedwaveforms in the guard bands allows no or tolerable interference withthe OFDM symbols in the data bands. Further, the spectrally containedwaveforms, for example using F-OFDM or OFDM/OQAM, have a smallerbandwidth than the guard bands.

In an embodiment, a synchronous secondary system uses F-OFDM symbols inthe guard bands. A UE uses synchronization signals from the primarysystem to synchronize communications for the secondary system. The UEmay be a secondary user of the secondary system, or a primary user ofthe primary system if the secondary system is used in signaling orcarrying other information for the primary system The UE can also useits own time-adjustment signals to perform synchronization. Using thesynchronization signals of the primary system for the second systemreduces overhead, since common signaling is exploited for the twosystems. Further, multiple guard bands can be used combined by a singleUE or multiple UEs. Alternatively, each guard band can be used by asingle UE or multiple UEs. In another embodiment, a synchronoussecondary system uses F-OFDM symbols in the guard bands. A UE usededicated synchronization signals to synchronize communications for thesecondary system. This increases overhead since additionalsynchronization signals are used for the secondary system, but allowsmore independence between the primary and secondary systems. Further,multiple guard bands can be used combined by a single UE or multipleUEs. Alternatively, each guard band can be used by a single UE ormultiple UEs.

Examples of the secondary system include machine-to-machine (M2M)systems, device-to-device (D2D) communications, or other systems thatcommunicate information independent of the primary information of theprimary system. In an embodiment, the secondary system communicationsare transmitted at lower power, such as using pico or femto cellsystems, relative to the first system communications. The twocommunications may serve different purposes. The two communications mayhave be of the same type (user data) but transmitted at different powerlevels or have different priority.

In another embodiment, the secondary system uses OFDM/OQAM for bothsynchronous and asynchronous communications. Multiple guard bands can beused (in combination) by a single UE or multiple UEs. Alternatively,each guard band can be used by a single UE or multiple UEs. Due to theuse of well localized pulse shapes in OFDM/OQAM, time asynchronizationmainly affects adjacent subcarriers. If a guard band is utilized bymultiple UEs in asynchronous mode, then one subcarrier between each pairof adjacent UEs is reserved as a guard in frequency. If a guard band isutilized by a single UE or multiple UEs in synchronous mode, then noreserved subcarriers are required in this guard band. Thisimplementation can have lower OOB radiation in comparison to F-OFDMdeployment. However, this OFDM/OQAM deployment can also have higherpeak-to-average power ratio (PAPR) in uplink and higher complexity.

FIG. 6 shows an embodiment of a method 600 for guard band utilizationfor synchronous and/or asynchronous communications. The method 600 canbe implemented by a UE, a base station or other transmitters in wirelessnetwork. At step 610, the network component transmits or receives OFDMsymbols within data bands assigned for primary communications.Specifically, the data bands are separated by guard bands, which havesmaller bandwidth than the data bands. The OFDM symbols can be F-OFDMsymbols. At step 620, the network component transmits or receives,within the guard bands, symbols for secondary communications. Thesymbols are modulated with a spectrally contained wave form according toOFDM modulation or according to joint OFDM and Offset QuadratureAmplitude Modulation (OQAM) modulation.

FIG. 7 is a block diagram of an exemplary processing system 700 that canbe used to implement various embodiments. For instance, the system 700may be part of a network component, such as a base station, a relay, arouter, a gateway, or a controller/server unit. Specific devices mayutilize all of the components shown, or only a subset of the componentsand levels of integration may vary from device to device. Furthermore, adevice may contain multiple instances of a component, such as multipleprocessing units, processors, memories, transmitters, receivers, etc.The processing system 700 may comprise a processing unit 701 equippedwith one or more input/output devices, such as a network interfaces,storage interfaces, and the like. The processing unit 701 may include acentral processing unit (CPU) 710, a memory 720, and a storage device730 connected to a bus. The bus may be one or more of any type ofseveral bus architectures including a memory bus or memory controller, aperipheral bus or the like.

The CPU 710 may comprise any type of electronic data processor. Thememory 720 may comprise any type of system memory such as static randomaccess memory (SRAM), dynamic random access memory (DRAM), synchronousDRAM (SDRAM), read-only memory (ROM), a combination thereof, or thelike. In an embodiment, the memory 720 may include ROM for use atboot-up, and DRAM for program and data storage for use while executingprograms. In embodiments, the memory 720 is non-transitory. The storagedevice 730 may comprise any type of storage device configured to storedata, programs, and other information and to make the data, programs,and other information accessible via the bus. The storage device 730 maycomprise, for example, one or more of a solid state drive, hard diskdrive, a magnetic disk drive, an optical disk drive, or the like.

The processing unit 701 also includes one or more network interfaces750, which may comprise wired links, such as an Ethernet cable or thelike, and/or wireless links to access nodes or one or more networks 780.The network interface 750 allows the processing unit 701 to communicatewith remote units via the networks 780. For example, the networkinterface 750 may provide wireless communication via one or moretransmitters/transmit antennas and one or more receivers/receiveantennas. In an embodiment, the processing unit 701 is coupled to alocal-area network or a wide-area network for data processing andcommunications with remote devices, such as other processing units, theInternet, remote storage facilities, or the like.

In accordance with an embodiment of the disclosure, a method increasingband utilization by a network component in a wireless network includesallocating secondary communications to a guard band. The guard bandseparates data bands assigned for primary communications and has asmaller bandwidth than the data bands. The method further includesmodulating, at the network component, symbols for the secondarycommunications with a spectrally contained wave form. The spectrallycontained wave form has a smaller bandwidth than the guard band. Thenetwork component transmits the modulated symbols for the secondarycommunications within the guard band. The method further includestransmitting data for the primary communications within the data bands.The primary communications and the secondary communications carryindependent information. The guard band has a smaller bandwidth than thedata bands. The modulating the symbols for the secondary communicationswith the spectrally contained wave form includes modulating the symbolsfor the secondary communications with orthogonal frequency-divisionmultiplexing (OFDM) or filtered OFDM (F-OFDM). The method furtherincludes synchronizing, at the network component, a timing of at least aportion of the secondary communications with transmissions of anothernetwork component. The transmitting includes transmitting thesynchronized secondary communications within the guard band. Thesecondary communications are synchronized according to synchronizationsignals for the primary communications. The secondary communications aresynchronized according to synchronization signals for the secondarycommunications and independent of transmissions of the primarycommunications. The modulating the symbols for the secondarycommunications with the spectrally contained wave form includesmodulating the symbols for the secondary communications with jointorthogonal frequency-division multiplexing (OFDM) and Offset QuadratureAmplitude Modulation (OQAM). The method further includes synchronizing atiming of at least a portion of the secondary communications withtransmissions of another network component. The transmitting includestransmitting the synchronized secondary communications within the guardband. The method further includes timing at least a portion of thesecondary communications to be asynchronous with transmissions ofanother network component. The transmitting includes transmitting theasynchronized secondary communications within the guard band. The guardband is shared by the network component and another network component,and a subcarrier shared between the network component and the othernetwork component is reserved in frequency for the guard band.

In accordance with another embodiment of the disclosure, a networkcomponent for increasing band utilization in a wireless network includesat least one processor and a non-transitory computer readable storagemedium storing programming for execution by the processor. Theprogramming includes instructions to allocate secondary communicationsto a guard band. The guard band separates data bands assigned forprimary communications and has a smaller bandwidth than the data bands.The programming further configures the network component to modulatesymbols for the secondary communications with a spectrally containedwave form. The spectrally contained wave form has a smaller bandwidththan the guard band. The network component is further configured totransmit the modulated symbols for the secondary communications withinthe guard band. The instructions to modulate the symbols for thesecondary communications with the spectrally contained wave form includeinstructions to modulate the symbols for the secondary communicationswith orthogonal frequency-division multiplexing (OFDM) or with jointOFDM and Offset Quadrature Amplitude Modulation (OQAM). The networkcomponent is a user equipment (UE). The secondary communications aremachine-to-machine (M2M) system communications. The secondarycommunications are device-to-device (D2D) communications. The secondarycommunications are lower power communications relative to the primarycommunications.

In accordance with another embodiment of the disclosure, a methodincreasing band utilization by a network component in a wireless networkincludes receiving secondary communications within a guard band. Theguard band separates data bands assigned for primary communications andhas a smaller bandwidth than the data bands. The network componentfurther detecting, in the received secondary communications, symbolsmodulated according to a spectrally contained wave form. The spectrallycontained wave form has a smaller bandwidth than the guard band. Themethod further includes receiving data for the primary communicationswithin the data bands. The detected symbols are orthogonalfrequency-division multiplexing (OFDM) symbols or filtered OFDM (F-OFDM)symbols. The detected symbols are joint orthogonal frequency-divisionmultiplexing (OFDM) and Offset Quadrature Amplitude Modulation (OQAM)symbols.

In accordance with yet another embodiment of the disclosure, a networkcomponent for increasing band utilization in a wireless network includesat least one processor and a non-transitory computer readable storagemedium storing programming for execution by the processor. Theprogramming includes instructions to receive secondary communicationswithin a guard band. The guard band separates data bands assigned forprimary communications and has a smaller bandwidth than the data bands.The programming includes further instructions to detect, in the receivedsecondary communications, symbols modulated according to a spectrallycontained wave form. The spectrally contained wave form has a smallerbandwidth than the guard band. The detected symbols are orthogonalfrequency-division multiplexing (OFDM) symbols or joint OFDM and OffsetQuadrature Amplitude Modulation (OQAM) symbols. The network component isa base station. The guard band is a dedicated guard band assigned to auser equipment (UE). The guard band is a shared guard band assigned tomultiple user equipments (UEs).

The foregoing has outlined rather broadly the features of an embodimentof the present invention in order that the detailed description of theinvention that follows may be better understood. Additional features andadvantages of embodiments of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for transmitting data in a communicationsystem, the method comprising: performing a first filtering operation ona first orthogonal frequency-division multiplexing (OFDM) symbol of afirst waveform to obtain a first filtered waveform; generating a firstspectrally contained OFDM waveform; generating a second spectrallycontained OFDM waveform; transmitting the first filtered waveform in afirst data band of a carrier; and transmitting the first spectrallycontained OFDM waveform and the second spectrally contained OFDMwaveform in a first guard band and a second guard band of the carrier,respectively, wherein the first data band is between the first guardband and the second guard band in the carrier.
 2. The method of claim 1,wherein the first guard band, the first data band, and the second guardband are consecutive bands in the carrier.
 3. The method of claim 1,wherein the transmitting the first spectrally contained OFDM waveformand the second spectrally contained OFDM waveform includes: transmittingthe second spectrally contained OFDM waveform synchronously orasynchronously with transmitting the first spectrally contained OFDMwaveform.
 4. The method of claim 1, wherein the first guard band and thesecond guard band each has a smaller bandwidth than the first data band.5. The method of claim 1, wherein the first spectrally contained OFDMwaveform has a smaller bandwidth than the first data band.
 6. The methodof claim 4, further comprising: transmitting the first filtered waveformin the first data band to a first node; and transmitting the firstspectrally contained OFDM waveform in the first guard band to a secondnode.
 7. The method of claim 6, wherein the first node is different thanthe second node.
 8. The method of claim 4, wherein the first spectrallycontained OFDM waveform is transmitted in the first guard band at alower power than the first filtered waveform in the first data band. 9.The method of claim 4, wherein the first guard band is positionedbetween the first data band and a second data band within a bandwidthrange.
 10. A transmitter for transmitting data in a communicationsystem, the transmitter comprising: at least one processor; and anon-transitory computer readable storage medium storing programming tobe executed by the at least one processor, the programming includinginstructions when executed by the at least one processor to: perform afirst filtering operation on a first orthogonal frequency-divisionmultiplexing (OFDM) symbol of a first waveform to obtain a firstfiltered waveform; generate a first spectrally contained OFDM waveform;generate a second spectrally contained OFDM waveform; transmit the firstfiltered waveform in a first data band of a carrier; and transmit thefirst spectrally contained OFDM waveform and the second spectrallycontained OFDM waveform in a first guard band and a second guard band ofthe carrier, respectively, wherein the first data band is between thefirst guard band and the second guard band in the carrier.
 11. Thetransmitter of claim 10, wherein the first guard band, the first databand, and the second guard band are consecutive bands in the carrier.12. The transmitter of claim 10, wherein the instructions to transmitthe first spectrally contained OFDM waveform and the second spectrallycontained OFDM waveform further include instructions when executed bythe at least one processor to: transmit the second spectrally containedOFDM waveform synchronously or asynchronously with transmitting thefirst spectrally contained OFDM waveform.
 13. The transmitter of claim10, wherein the first guard band and the second guard band each has asmaller bandwidth than the first data band.
 14. The transmitter of claim10, wherein the first spectrally contained OFDM waveform has a smallerbandwidth than the first data band.
 15. The method of claim 1, furthercomprising: generating a third spectrally contained OFDM waveform; andtransmitting the third spectrally contained OFDM waveform in a combinedband of the second guard band and a third guard band to a first node,wherein the first guard band, the first data band, the second guardband, the third guard band, and a second data band are consecutive bandsin the carrier.
 16. The method of claim 1, wherein synchronizationsignals in the first data band are used to synchronize communicationsfor the first guard band.
 17. The method of claim 1, the firstspectrally contained OFDM waveform is transmitted in the first guardband with a lower priority than the first filtered waveform in the firstdata band.